U.S. patent number 6,680,536 [Application Number 10/106,210] was granted by the patent office on 2004-01-20 for probe unit having resilient metal leads.
This patent grant is currently assigned to Yamaha Corporation. Invention is credited to Atsuo Hattori, Shuichi Sawada, Masahiro Sugiura, Yoshiki Terada.
United States Patent |
6,680,536 |
Hattori , et al. |
January 20, 2004 |
Probe unit having resilient metal leads
Abstract
A probe unit has a plurality of metal leads regularly juxtaposed
on the surface of a substrate. Each metal lead has a resilient
contact piece in a front portion of the lead, the resilient contact
piece being spaced apart from the substrate surface or extending
over an edge of the substrate. The cross sectional shape of the
resilient contact piece is an arc shape and/or has a projection
near at the distal end of the resilient contact piece.
Inventors: |
Hattori; Atsuo (Iwata,
JP), Sawada; Shuichi (Hamamatsu, JP),
Sugiura; Masahiro (Hamamatsu, JP), Terada;
Yoshiki (Hamamatsu, JP) |
Assignee: |
Yamaha Corporation
(JP)
|
Family
ID: |
18947074 |
Appl.
No.: |
10/106,210 |
Filed: |
March 27, 2002 |
Foreign Application Priority Data
|
|
|
|
|
Mar 28, 2001 [JP] |
|
|
2001-092645 |
|
Current U.S.
Class: |
257/739; 257/773;
257/776; 438/14; 438/52 |
Current CPC
Class: |
G01R
1/06738 (20130101); G01R 3/00 (20130101); H05K
3/4092 (20130101); H01L 2924/0002 (20130101); H01L
2924/0002 (20130101); H01L 2924/00 (20130101) |
Current International
Class: |
G01R
1/067 (20060101); H05K 3/40 (20060101); H01L
023/48 () |
Field of
Search: |
;438/14,52,17,48
;257/739,773,776,784 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
2-176570 |
|
Jul 1990 |
|
JP |
|
4-363671 |
|
Dec 1992 |
|
JP |
|
8-220140 |
|
Aug 1996 |
|
JP |
|
11-133062 |
|
May 1999 |
|
JP |
|
11-237406 |
|
Aug 1999 |
|
JP |
|
Primary Examiner: Everhart; Caridad
Attorney, Agent or Firm: Dickstein, Shapiro, Morin &
Oshinsky, LLP.
Claims
What we claim are:
1. A probe unit comprising: a substrate having an insulated
surface; and a plurality of metal leads on said insulating surface
of said substrate, each said metal lead including a base portion
and a resilient contact piece extending from one end of said base
portion, said base portion contacting said insulated surface along
said base portion's entire length, said resilient contact piece
being spaced apart from said insulated surface along said contact
piece's entire length, said resilient contact piece having a cross
section taken along a plane which is perpendicular to said
insulated surface and which defines a smooth arcuate shape over
substantially said entire length of said resilient contact
piece.
2. A probe according to claim 1, further comprising a small
projection formed on a surface of said resilient contract piece on
a side of said resilient contact piece facing opposite to said
substrate near at a distal end of said resilient contact piece.
3. A probe unit according to claim 1, wherein an arcuate bump is
located near the distal end of said resilient contact piece.
4. A probe unit according to claim 1, further comprising through
holes formed through said substrate at positions where said
substrate contacts said metal leads, and wherein via conductors
filled said through holes.
5. A probe unit according to claim 1, said resilient contact piece
has a thickness which is generally uniform over its entire
length.
6. A probe unit according to claim 1, wherein said metal leads are
regularly juxtaposed on said insulated surface.
7. A probe unit comprising: a substrate having an insulated
surface: a plurality of metal leads regularly juxtaposed on said
insulated surface of said substrate, each said metal lead having a
resilient contact piece having a width W in a front portion of said
lead, the resilient contact piece extending over an edge of said
substrate; and a projection formed in said resilient contact piece
at a distal end thereof, said projection extending in a direction
away from said substrate and having a surface shape constituting a
portion of a sphere, said projection having a length 2R, wherein
2R>W.
8. A probe unit comprising: a substrate having an insulated
surface: a plurality of metal leads regularly juxtaposed on the
insulated surface of said substrate, said metal lead having a
resilient contact piece in a front portion of said lead, the
resilient contact piece extending over an edge of said substrate;
and a plurality of small projections formed on a surface of the
resilient contact piece near at a distal end thereof on a side
opposite to said substrate, said small projections having the same
shape.
9. A probe unit according to claim 8, wherein said small projection
has a surface shape constituting a portion of a spherical
surface.
10. A probe unit according to claim 8, wherein said small
projection has a surface shape constituting a portion of a
cylindrical surface.
11. A probe unit comprising: a substrate having an insulated
surface: a plurality of metal leads regularly juxtaposed on the
insulated surface of said substrate, said metal lead having a
resilient contact piece in a front portion of said lead, the
resilient contact piece extending over an edge of said substrate;
and two projections formed on a surface of the resilient contact
piece near at a distal end thereof, in symmetry with a center line
of said metal lead along a longitudinal direction thereof, said two
projections becoming higher at a position nearer to the edge of the
resilient contact piece and having a shape that the projections
become higher and skirts of the projections become nearer, from the
distal end to a side of said substrate at least up to an
intermediate position.
12. A probe unit according to claim 11, wherein the resilient
contact piece has a shape which has a shape of the skirts of said
two projections in an area from the distal end to a position where
the two projections become nearest and a U-character shaped
retracted shape between the two projections.
13. A method of manufacturing a probe unit comprising: a bumping
bar on one surface of a substrate, said bumping bar having a curved
surface, a cross section of said curved surface lying perpendicular
to said surface of said substrate having the shape of a smooth arc;
forming leads on said surface of said substrate, a distal end of
each lead riding on said bumping bar, so that a portion of each
lead riding on said bumping bar is curved in a smooth shape; and
removing said bumping bar after said leads are formed.
14. A method of manufacturing a probe unit comprising: a step of
preparing a substrate having a recess formed in a surface layer: a
step of forming a sacrificial filled in the recess; a step of
forming a bumping bar having a predetermined pattern on the
sacrificial layer: a step of forming leads on a surface of the
substrate, a distal end of each lead riding on the bumping bar; a
step of forming a cut extending from a bottom of the substrate into
the sacrificial layer; and a step of etching and removing the
sacrificial layer and bumping bar.
Description
CROSS REFERENCE TO RELATED APPLICATION
This application is based on and claims priority of Japanese patent
application No. 2001-92645, filed on Mar. 28, 2001, the whole
contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
A) Field of the Invention
The present invention relates to a probe unit to be used for a
conduction test of an electronic component such as a semiconductor
integrated circuit and a liquid crystal panel by making the probe
unit in contact with the electrodes or terminal unit of the
electronic component.
B) Description of the Related Art
Electronic components such as large scale semiconductor integrated
circuits (LSI), liquid crystal panels and printed circuit boards
are generally subjected to a conduction test in order to check
whether electronic components operate normally in the manner
written in the specification. LSI is formed on a silicon substrate.
A liquid crystal panel is formed by using a pair of glass
substrates. A printed circuit board is formed on a fiber reinforced
plastic (FRP) substrate or a polyimide substrate. On these
substrates a plurality of electrodes are formed being
juxtaposed.
The conduction test is performed by pushing elastic or resilient
beams in the front portions of leads of a probe unit against the
electrodes on the substrate of an electronic component.
There is a tendency that a pitch of electrodes is becoming finer. A
pitch of resilient beams of a probe unit is required to be
correspondingly finer.
The pitch of electrodes is presently 0.1 mm or narrower. It is
difficult to form a probe unit having such a pitch by a mechanical
punching work. Etching or plating has been adopted to form such a
probe unit.
For example, JP-A-11-133062 discloses a probe card having leads
with contact terminals disposed along the principal surface of the
substrate and extending over the edge of the substrate. These leads
are coupled to the substrate via a holder unit having a
predetermined height. A contact terminal of quadrilateral pyramids
is disclosed.
JP-A-8-220140 proposes: a probe card having conductive projections
of a pyramid shape having a pointed tip; and a method of
manufacturing a probe card by forming a projection by transferring
a projection formed by a mold, or fixing a fine conductive wire to
a substrate and thereafter cutting the wire.
JP-A-4-363671 proposes a probe board which is manufactured by
forming projecting contacts on the end portions of wiring patterns
formed on a flexible wiring board, forming resilient members on the
bottom surface of the board, and forming slits through the board to
separate each of the wiring patterns. The projecting contact has a
pointed tip directed toward a contact unit.
JP-A-11-237406 discloses a plated test probe to be made in
electrical contact with a solder ball on an integrated circuit
device.
JP-A-2-176570 proposes a probe card whose end portions are made in
contact with electrodes and has a recess into which the electrodes
are inserted.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a probe unit
and its manufacture method capable of efficiently inspecting the
conduction characteristics of a highly integrated electronic
component.
It is another object of the present invention to provide a probe
unit and its manufacture method suitable for inspecting parallel
wiring lines of an electronic component and capable of dealing with
some position misalignment of the probe unit, without damaging the
wiring lines during inspection and without damaging probes during
manufacture.
According to one aspect of the present invention, there is provided
a probe unit comprising: a substrate having an insulated surface;
and a plurality of metal leads regularly juxtaposed on the
insulated surface of the substrate, the metal lead having a
resilient contact piece in a front portion of the lead, the
resilient contact piece being spaced apart from the insulated
surface or extending over an edge of the substrate, and a vertical
cross sectional shape of the resilient contact piece along a
longitudinal direction of the metal lead having a portion curved in
an arc shape.
According to another aspect of the present invention, there is
provided a probe unit comprising: a substrate having an insulated
surface; a plurality of metal leads regularly juxtaposed on the
insulated surface of the substrate, the metal lead having a
resilient contact piece in a front portion of the lead, the
resilient contact piece extending over an edge of the substrate;
and a projection formed on a surface of the resilient contact piece
at a distal end thereof, the projection protruding from the surface
of the resilient contact piece toward a direction opposite to the
substrate and having a surface shape constituting a portion of a
sphere.
According to a further aspect of the present invention, there is
provided a probe unit comprising: a substrate having an insulated
surface; a plurality of metal leads regularly juxtaposed on the
insulated surface of the substrate, the metal lead having a
resilient contact piece in a front portion of the lead, the
resilient contact piece extending over an edge of the substrate;
and a plurality of small projections formed on a surface of the
resilient contact piece near at a distal end thereof on a side
opposite to the substrate, the small projections having the same
shape.
According to a still further aspect of the present invention, there
is provided a probe unit comprising: a substrate having an
insulated surface; a plurality of metal leads regularly juxtaposed
on the insulated surface of the substrate, the metal lead having a
resilient contact piece in a front portion of the lead, the
resilient contact piece extending over an edge of the substrate;
and two projections formed on a surface of the resilient contact
piece near at a distal end thereof, in symmetry with a center line
of the metal lead along a longitudinal direction thereof, the two
projections becoming higher at a position nearer to the edge of the
resilient contact piece and having a shape that the projections
become higher and skirts of the projections become nearer, from the
distal end to a side of the substrate at least up to an
intermediate position.
If the resilient contact piece is spaced apart from the substrate,
the resilient contact piece can be curved toward the substrate side
when the resilient contact piece is pushed against the electrode to
be inspected. It is possible to prevent an excessive force from
being applied to the electrode, and the electrode is rarely
damaged.
If the resilient contact piece is formed curving in an arc shape,
stress of the resilient contact piece can be easily controlled.
A plurality of juxtaposed resilient contact pieces can be pushed at
the same time against a plurality of electrodes disposed at the end
of an electronic component such as an integrated circuit device.
This probe unit is suitable for inspecting juxtaposed wiring
leads.
An uniform load can be applied to each resilient contact piece at a
predetermined bending amount.
A dot can be formed integrally with the resilient contact piece
near at its front end portion. It is rare that only the dot is
missed.
If the dome-shaped projection is formed at the front portion of the
resilient contact piece, the resilient contact piece pushing an
electrode hardly damages plated gold or copper wiring leads because
the resilient contact piece has no edge.
If a dome-shaped or elongated small dot is formed on both sides of
the resilient contact piece, the contact positions of the electrode
and resilient contact piece can be automatically corrected from the
displaced contact positions.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1A, 1B, 1C and 1D are schematic cross sectional views showing
examples of a curved resilient contact piece in a front portion of
a lead formed on a substrate, the resilient contact piece extending
over the edge of the substrate.
FIGS. 2A, 2B and 2C are a plan view and cross sectional views
showing examples of a resilient contact piece extending over the
edge of a substrate, the resilient contact piece having a curved
front portion, and FIG. 2D is a perspective view illustrating how a
probe unit is used.
FIGS. 3A, 3B, 3C and 3D are plan views and cross sectional views
showing examples of a resilient contact piece having a dome-shaped
projection in the front portion.
FIGS. 4A, 4B and 4C are perspective views showing examples of a
resilient contact piece having a plurality of small dots on the
surfaces thereof.
FIGS. 5A, 5B and 5C are perspective views showing other examples of
a resilient contact piece having a plurality of small elongated
dots on the surfaces thereof.
FIGS. 6A and 6B are a plan view and a side view showing an example
of a resilient contact piece having projections on both sides of
the distal end of the resilient contact piece.
FIGS. 7A and 7B are a plan view and a side view showing another
example of a resilient contact piece having projections on both
sides of the distal end of the resilient contact piece.
FIGS. 8A and 8B a plan view showing the shape of a probe unit and a
perspective view illustrating how the probe unit is used.
FIGS. 9A, 9B and 9C are cross sectional views illustrating several
methods of forming a resilient contact piece.
FIGS. 10A, 10B, 10C, 10D and 10E are cross sectional views and a
plan view illustrating manufacture processes for probes.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Description will be made on the preferred embodiments of the
invention, referring to the drawings. FIGS. 1A, 1B, 1C and 1D are
cross sectional views showing examples of the structure of a probe
unit.
As shown in FIG. 1A, a metal lead 2 is disposed on the surface of a
substrate 1, a front portion of the metal lead extends above the
surface of the substrate to form a resilient contact piece 3.
The substrate 1 may be any one of a glass plate, a ceramic plate, a
synthetic resin plate, a silicon plate and a metal plate. If an
electroconductive substrate such as a metal plate is used, an
insulating layer is formed on the surface where leads are to be
formed.
A number of metal leads 2 are regularly disposed on the surface of
the substrate 1.
The metal leads may be disposed in parallel or regularly at
predetermined angles.
The resilient contact piece 3 of each metal lead 2 is formed in the
front portion of the lead along the longitudinal direction. A
plurality of resilient contact pieces are disposed at the same
position in the longitudinal direction or at regularly changing
different positions, respectively with the same shape and size. The
position, shape and length of each resilient contact piece may be
changed in various ways.
The metal lead 2 has generally a uniform thickness over the whole
length thereof, both in a portion contacting the substrate 1 and in
a portion of the resilient contact piece spaced apart from the
substrate 1. The resilient contact piece 3 spaced apart from the
surface of the substrate 1 extends in a smooth arc shape and has
its distal end near at the remotest point from the surface of the
substrate 1. The position near at the remotest point is a position
capable of providing the same function as that at the remotest
point.
The planar shape of the distal end of the resilient contact piece 3
may be angled like a rectangle, rounded like a semicircle, or a
rectangle whose corners are rounded. It is preferable that the
metal lead 2 has a proper rigidity and elasticity. The metal lead
is preferably made of Ni, Ni--Fe alloy, Ni--W alloy or metal glass.
The thickness of the metal lead 2 is preferably about 10 to 80
.mu.m in order to give a proper strength and elasticity.
The probe unit may have a small projection near at the distal end
of each resilient contact piece 3. The shape of the dot is not
limited to a particular one.
FIG. 1B shows an example of a small projection 6 formed on a
resilient contact piece 3 near at the distal end on the surface
opposite to the substrate 1. FIG. 1C shows an example of a small
projection of an arc shape whose radius of curvature is smaller
than that of the resilient contact piece 3, or preferably the small
projection has a semisphere shape. These projections are made of
the same material as that of the metal lead 2 or of a different
material. If a different material is to be used, metals having
affinity are used. The metal has preferably a proper rigidity.
As shown in FIG. 1D, an upward curved resilient contact piece 3 may
have a small projection on the top surface (remotest from the
substrate) of the resilient contact piece, the small projection
being curved at a smaller radius of curvature than the resilient
contact piece.
As shown in FIGS. 1A to 1D, a through hole 5 may be formed through
the substrate 1 where each metal lead 2 contacts the substrate to
fill a metal via 4 in the through hole 5. In this case, a signal
(current) flowing through the metal lead 2 can be picked up at the
bottom surface of the substrate.
Since the resilient contact piece 3 is spaced apart from the
substrate 1, the resilient contact piece 3 is curved toward the
substrate at a proper elasticity when the piece is abutted on an
electrode to be inspected. Since an excessive force is not applied
to the electrode, it is rare to damage the electrode. Since the
resilient contact piece is curved in an arc shape and has generally
a uniform thickness, it is easy to control stress.
If the resilient contact pieces disposed in parallel have the same
shape and size and are disposed at the same position along the
longitudinal direction of the metal lead 2, the resilient contact
pieces of the probe can be pushed at the same time against a number
of electrodes juxtaposed at the end of, for example, an integrated
circuit, and a uniform load can be applied to each resilient
contact piece at a predetermined bending force. It is possible to
prevent only some resilient contact pieces from being pushed
strongly against the electrodes.
The resilient contact pieces are generally directed toward a sample
to be inspected. If the metal via 4 formed through the substrate 1
is provided to pick up a signal on the lead 2 from the bottom
surface of the substrate, lead wire electrodes, insulating films
between lead wire electrodes and the like can be formed on the
bottom surface of the substrate instead of the front surface
thereof.
FIG. 2A shows an example of a probe unit in which a plurality of
metal leads 2 regularly disposed in parallel on the surface of a
substrate extend outwardly over the edge of the substrate 1.
As shown in FIG. 2A, one end 3 of the metal lead 2 protrudes
outwardly over the edge of the substrate 1. The cross sectional
shape of the front portion 3 may be an arc shape as shown in FIG.
2B or may have an arc shaped intermediate portion in a straight
beam as shown in FIG. 2C.
In this probe unit, a plated pad 7 of gold or lamination of gold
and platinum may be formed on an end portion of the lead 2 opposite
to the resilient contact piece 3. A thickness of the plated pad 7
is preferably about 4 to 5 .mu.m.
The lead 2 in tight contact with the substrate 1 near at the plated
pad may be covered with a protective film to enhance the tight
contactness of the lead 2 to the substrate 1 (prevention of lead
peel-off) and to prevent electric shortage between leads.
These resilient contact pieces have the characteristics similar to
those of the resilient contact pieces of the probe unit described
earlier, and can be used in the similar manner. Instead of
directing the probe unit in a horizontal posture toward the
component to be inspected, the probe unit is set upright to push
downward the distal ends of the resilient contact pieces against
the electrodes of a component such as an integrated circuit.
FIG. 2D is a diagram illustrating how the probe unit is used by
setting it upright. A connector 16 connected to the metal leads is
mounted on the probe unit, and the resilient contact pieces are
pushed downward to measure the component 17.
The resilient contact pieces are pushed downward against the
electrodes of an integrated circuit by setting one end of the probe
unit along the longitudinal direction perpendicular to the surface
of the integrated circuit substrate. Since the resilient contact
piece 3 has a bending portion, it is deformed by stress so that the
probe is given elasticity.
By providing the plated pads, the electrical resistance between the
probe and external wiring lines can be lowered, and reliability of
attachment of solder plating or anisotropically conductive film can
be improved.
FIGS. 3A, 3B, 3C and 3D are plan views and cross sectional views
showing examples of a probe unit according to another embodiment of
the invention.
Referring to FIG. 3A, a resilient contact piece 3 extends over the
edge of a substrate 1. A dome-shaped projection (forming part of a
sphere) 6 is formed at the distal end of a resilient contact piece
3 of the probe. In the example shown in FIG. 3A, the diameter of a
sphere is equal to the width of the lead 2, and in the example
shown in FIG. 3C, the diameter 2R of a circle obtained by cutting a
sphere along a plane defined by the lead upper surface is greater
than the width W of the lead 2. As shown in FIGS. 3B and 3D, the
projection 6 of the resilient contact piece 3 has a cross sectional
shape which makes the lead 2 bend upward. In FIG. 3D, 2r is a
diameter of a circle obtained by cutting the spherical surface of a
concave portion by a plane defined by the bottom surface of the
lead 2 (substrate surface). The projection on the upper surface of
the resilient contact piece is a portion of a spherical surface
including a circle having the diameter 2R, and the concave portion
under the resilient contact piece is a portion of a spherical
surface including a circle having the diameter 2r. Both the
spherical surfaces have generally the same center.
The relation between 2R and W is preferably 2R>W, and the
relation between 2r and W is preferably 2r>W. For example, if W
is 25 .mu.m, 2R may be 60 .mu.m and 2r may be 40 .mu.m. Other
values may also take.
In FIGS. 3A to 3D, a hollow is formed under the dome-shaped
projection 6. Although the distal end portion has a dome-shaped
projection, the hollow may not be formed.
With this probe unit, a conduction test is performed by pushing the
dome-shaped projections 6 against the electrodes of a component to
be inspected. Since the dome-shaped projections are used, corners
are rarely abutted on the electrodes so that the electrodes are
hardly damaged.
If the resilient contact piece itself has edges or if the
projection and curved portion of the resilient contact piece have
edges, and if the edges are pushed against the electrodes of a
component to be inspected, because of some position misalignment of
the probe and electrode, the plated gold or copper wiring leads of
the electrodes may be damaged. If the flat or curved portions of
the resilient contact piece is abutted on the electrode, the
electrode will not be damaged. Since the dome-shaped projections
without any edge are formed at the end of the probe as in this
embodiment, the plated gold or copper wiring leads of the
electrodes will not be damaged even if an integrated circuit
substrate has an irregular surface, even if the substrate is
slanted, or even if the probe and electrodes are misaligned.
If the relations of 2R, 2r and W satisfy the above-described
conditions, the gold plated copper wiring lead will not be damaged,
a sufficient contact area can be obtained, and a contact resistance
can be lowered.
FIGS. 4A, 4B and 4C show examples of a resilient contact piece 3
having a plurality of small dots of the same shape formed on the
distal end portion of the resilient contact piece 3. In the
examples shown in FIGS. 4A to 4C, a small dot 8 has a shape of a
partial sphere, i.e., a dome-shaped small dot. In the examples
shown in FIGS. 5A, 5B and 5C, instead of a sphere, a
semicylindrical small dot 8 is used. This small dot 8 has a shape
obtained by cutting a cylinder in parallel to its axis, the cut
surface being in contact with the surface of the resilient contact
piece. In these embodiments, the shape of the distal end of the
resilient contact pieces 3 is semicircle in the plane parallel to
the surface of the resilient contact piece 3. The shape is not
limited only to a semicircle.
In the example shown in FIG. 4A, dome-shaped small dots are
disposed in three rows, in the central area and near at the
opposite sides along the lead width direction. In the example shown
in FIG. 4B, dome-shaped small dots are disposed in two rows near at
the opposite sides. In the example shown in FIG. 4C, dome-shaped
small dots 8 are disposed at three positions, in the central area
near at the distal end of the resilient contact piece 3 and near at
the opposite sides near the distal end.
In the example shown in FIG. 5A, semicylindrical small dots 8 are
disposed in the central area and near at the opposite sides near
the distal end along the width direction of the lead 2. In the
example shown in FIG. 5B, semicylindrical small dost 8 are disposed
at the opposite sides. In the examples shown in FIGS. 5A and 5B,
the longitudinal direction of the semicylindrical small dots 8 is
disposed in parallel to the longitudinal direction of the metal
lead 2. In the example shown in FIG. 5C, a plurality of
semicylindrical small dots are disposed with their longitudinal
direction being set perpendicular to the longitudinal direction of
the lead.
Electrodes of a component to be inspected have generally a
trapezoidal cross section having a flat upper surface and the side
walls increasing its width toward the substrate. When a component
is inspected by abutting the resilient contact pieces on the
electrodes having such a shape and if only one large projection is
formed on each resilient contact piece, there is no problem if the
front end of the projection abuts on the upper flat surface of the
electrode, even if the positions of the probe and electrode are
displaced to some degree. However, if the projection displaces from
the upper flat surface of the electrode, the probe may slips down
on the electrode side wall.
However, if a plurality of small dots 8 are formed in the distal
end area of the resilient contact pieces 3, it is possible to
prevent the probe from slipping down on the side wall of the
electrode if other small dots ride on the upper flat surface of
electrodes even if the probe distal end portion displaces along a
direction perpendicular to the lead longitudinal direction.
Good contact between the probe and electrodes is possible even if
the probe distal end portion displaces along the lead longitudinal
direction, in the case as shown in FIGS. 5A and 5B that the small
dots 8 are semicylindrical and the longitudinal direction is
parallel to the lead longitudinal direction, in the case as shown
in FIG. 5C that the small dots are semicylindrical and the
longitudinal direction is perpendicular to the lead longitudinal
direction, and in the case as shown in FIGS. 4A and 4B that a
plurality of dome-shaped small dots are disposed along the lead
longitudinal direction.
FIGS. 6A and 6B are a plan view and a side view showing another
embodiment of the invention. FIGS. 7A and 7B are a plan view and a
side view showing an example of another structure.
Projections 6 are formed on both sides of a resilient contact piece
3 at the distal end, the resilient contact piece 3 extending over
the edge of a substrate 1. The projection 6 has a shape that the
lead is pushed upward along a portion of a virtual spherical
surface indicated by a broken line. In other words, it has a shape
that it includes a portion of a dome-shaped projection.
Therefore, the projection 6 becomes higher at a nearer position to
the center of the virtual circle shown by the broken line, and the
skirts of the projections on both sides become nearer to each other
at least up to the intermediate position along a line from the
central distal end of the resilient contact piece 3 toward the
proximal end.
In the example shown in FIG. 6A, the distal end of the resilient
contact piece 3 is circular.
In the example shown in FIG. 7A, the distal end of the resilient
contact piece 3 is constituted of the skirts of two projections 6.
The distal end retracts in conformity with the shape of the skirts
of the projections 6 until the projections become nearest, and
retracts further from the nearest position to form a U-character
shaped dent. In the distal end shape shown in FIGS. 7A and 7B, it
is preferable that the distance between two projections is
relatively narrow.
In the examples shown in FIGS. 6B and 7B, a dent corresponding to
the projection 6 is formed under the projection at the distal end
portion of the resilient contact piece. The lead 2 including the
projections 6 has generally a uniform thickness, which is easy to
fabricate. This dent may not be formed. A fabrication method of
forming the projections 6 on the lead 2 may be adopted.
If the width of the upper flat surface of an electrode of a
trapezoidal shape is narrower than the distance between the
projections at the distal end portion of the resilient contact
piece, the flat surface (flat valley surface) between projections
becomes in contact with the upper flat surface of the electrode. If
the probe distal end displaces laterally, the side of the upper
flat surface of the electrode abuts on the wall of the projection.
As the probe is further pushed against the electrode, a force which
moves the probe laterally is generated so that the distal end of
the probe is moved to make the upper flat surface of the electrode
be in contact with the flat valley surface of the probe, as in the
normal case. In this manner, an inspection method capable of
automatically correcting a position displacement can be
realized.
If the width of the upper flat surface of an electrode of a
trapezoidal shape is wider than the distance between the
projections at the distal end portion of the resilient contact
piece, the curved side walls of the two projections abut on the
opposite sides of the upper flat surface of the electrode to
realize a stable normal contact. If the probe distal end displaces
laterally, one side of the upper flat surface of the electrode
abuts on the wall of one projection. As the probe is further pushed
against the electrode, a force which moves the probe laterally is
generated so that the distal end of the probe is moved to make both
sides of the upper flat surface of the electrode be in contact with
the curved side walls of the projections as in the normal case.
Also in this manner, an inspection method capable of automatically
correcting a position displacement can be realized.
Each of the leads described above can use the same material and can
set the same thickness as those of the embodiments described
earlier. The width and pitch of juxtaposed leads and the length of
a resilient contact piece can be selected properly in accordance
with the electrode layout of a component such as an integrated
circuit to be inspected.
In each of the probe units described above, a wiring lead is
connected to the surface of each lead on the side opposite to the
lead resilient contact piece, or to the metal via connected to the
lead surface through the substrate. This wiring lead can be
connected by a wiring process used by a usual probe unit.
It is obvious that the structure common to the embodiments
described earlier provides similar effects to be given by the
structure.
FIG. 8A is a plan view showing an example of a probe unit, and FIG.
8B is a perspective view illustrating how the probe unit is used.
In FIG. 8A, reference numeral 18 represents a wiring lead, and in
FIG. 8B, reference numeral 17 represents a component to be
inspected.
Next, a method of manufacturing a probe unit of each of the
above-described embodiments will be described.
As shown in FIG. 9A, a bumping bar 9 is formed on a substrate 1 at
a predetermined position by using resist, low melting point glass
such as PSG, BSG and BPSG, or refractory metal such as Pb, Sn and
In.
The substrate may be a substrate of any type which is widely used
in this field. If an electroconductive substrate is to be used, an
insulating film is formed on the surface of the substrate.
The cross sectional shape of the bumping bar 9 along the
longitudinal direction of a lead to be formed on the substrate 1 is
an arc shape having a smooth upper surface. This bumping bar 9 is
preferably a semicylindrical projection extending in the same shape
along a direction perpendicular to the lead.
This shape can be obtained in the following manner. If resist is to
be used, resist is coated to a predetermined thickness in an
elongated pattern, and heated to soften it and fluidize the corners
thereof. If low melting glass or refractory metal is to be used
instead of resist, the shape can also be obtained through heating
and softening. If resist is used, it is thereafter baked to harden
it.
Next, a plating underlayer (hereinafter called a probe plating
underlayer) is formed on the whole surface of the substrate formed
with the bumping bar. In order to improve tight adhesion of the
probe underlayer to the substrate, the substrate may be etched by
about 10 angstroms by using ion gas, before the underlayer is
formed.
Next, a resist mask PR is formed on the substrate to expose the
plating underlayer corresponding to the portion where probe leads
are to be formed.
The resist mask PR is formed so that the front portion of each
probe lead rides on the bumping bar 9. With this setting, the front
portion of a probe lead 2 is curved and spaced apart from the
substrate at the later process.
Electroplating is performed relative to the surfaces of the exposed
probe plating underlayer layer, by using, for example, plating
liquid having sulfuric acid as its base composition. The plated
layer is therefore grown and leads are formed. Thereafter, the
resist mask PR is removed.
The plating underlayer and bumping bar 9 in the area where the
leads are not to be formed are removed by milling, resist remover,
or ashing. Leads having resilient contact pieces at their front
portions and spaced apart from the substrate are therefore formed
being juxtaposed on the substrate.
Alternatively, the probe plating underlayer may be formed on the
substrate with the bumping bar by using resist only in the areas
where the probes are to be formed. Also in this case, the resist
mask is formed so that the front portion of each probe lead rides
on the bumping bar 9.
In forming the probe plating underlayer, known pattern forming
methods can be utilized, such as a method of forming a probe metal
layer on the substrate whole surface and pattering it by a photo
etching process using resist and a method of printing
electroconductive paste on the substrate. There are several methods
of forming dots 6 on the distal end portion of the resilient
contact piece 3.
As shown in FIG. 9B, after the leads are formed, a shielding
pattern of resist 10 is formed on the substrate in the area where
the dots of the resilient contact pieces 3 are not to be formed.
Thereafter, metal is sputtered to form dots 6. Instead of
sputtering, plating may be used for forming the dots 6.
If metal is sputtered by about 5 .mu.m, a dot 6 can be formed on
the resilient contact piece 3 at the predetermined position. The
metal layer 11 is also formed during sputtering on the resist 10.
The metal may be the same as the metal of leads, or different metal
having a proper rigidity.
Next, the resist 10 is removed by, for example, hot
N-methyl-2-pyrrolidone. Resist can be removed more easily by using
an ultrasonic vessel.
The resist may be removed by using a plasma ashing system.
If the bumping bar 9 of the substrate is made of resist, this bar 9
can be removed at the same time when the resist removing process is
performed. If the bumping bar 9 is made of low melting glass or
refractory metal, the bar can be removed by milling and a lead
whose front portion is curved and having dots near at the distal
end of the lead can be obtained.
FIG. 9C illustrates a method of forming a lead having a dent under
the resilient contact piece. On a semicylindrical bumping bar 9, a
small dot 9A having the surface similar to a spherical portion is
formed by using resist or the like. Thereafter, similar to FIG. 9A,
electroplating is performed to form a lead layer 2. The lead layer
having a curved portion and a small dot projecting from the curved
portion can be formed, the lead layer having generally the uniform
thickness. Thereafter, the resist patterns PR, 9A and 9 are
removed.
If a signal (current) flowing through each metal lead is to be
picked up from the bottom surface of the substrate by forming a
conductive via through the substrate where the metal lead contacts,
a plurality of through holes are formed through the substrate at
predetermined positions before the bumping bar is formed on the
substrate surface.
If the substrate is a ceramic plate, through holes may be formed
through the ceramic plate still not baked by using a punching
machine, or they may be formed through the baked ceramic plate by
CO.sub.2 laser or sand blast. If the substrate is a silicon
substrate, through holes may be formed by reactive ion etching and
thereafter an oxide film is formed on the substrate surface. If the
substrate is a metal surface, through holes are formed by a cutting
work and thereafter an insulating film is formed on the substrate
surface. If the substrate is a chemically cutting type
photosensitive glass plate, an ultraviolet ray is applied only to
the areas where through holes are to be formed, and after a heat
treatment, the substrate is selectively etched by dilute
hydrofluoric acid to form through holes.
Next, a metal layer 5 is filled in the through holes by filling
metal paste such as copper paste in the through holes. Solvent
contained in the metal paste filled in the through hole is
evaporated by heating to form the metal layer. When the metal layer
is formed, this layer is contracted. By considering this
contraction, excessive metal paste is filled in the through hole to
such an extent that the metal paste overflows the through hole. The
substrate with the metal paste filled in the through hole is heated
to change the metal paste layer to a metal layer. Then, the
overflowed metal is polished and removed to form the flat surface
of the substrate with the metal layer filled in the through
hole.
A plated pad of gold or a lamination of gold and platinum may be
formed on the bottom of a through hole. In this case, the substrate
is covered with a resist pattern exposing the area where the plated
pad is to be formed, and gold or gold and platinum are plated to
about 4 to 5 .mu.m to form the plated pad.
If the through hole is not formed, a plated pad may be formed in a
manner similar to that described above on the surface of the
proximal end portion of the lead on the side opposite to the
resilient contact piece.
If an area where the lead is tightly adhered to the substrate is
covered with a protective film in order to enhance the tight
adhesion between the lead and substrate, photosensitive polyimide,
ultraviolet hardening adhesive, cardo type insulating film,
photoresist or the like is coated on the lead excepting the plated
pad and hardened.
Next, an example of a probe unit manufacturing method according to
another embodiment will be described.
FIGS. 10A to 10E are schematic diagrams showing an embodiment of
the manufacture method.
As shown in FIG. 10A, a recess 12 is formed in one surface layer of
a substrate 1.
Similar to the above-described embodiments, the substrate may be a
substrate of any type which is used widely in this field. If an
electroconductive substrate is used, an insulating film is formed
on the substrate surface.
It is preferable to form this recess 12 to be parallel to one side
of the substrate and straight.
This recess 12 has a predetermined depth and width and extends from
one side of the substrate to the opposing side. This recess may
traverse the substrate when it is first formed, or a recess is
formed extending over the width at least wider than the probe unit
and thereafter, the substrate is cut along lines traversing the
recess and in parallel to the lead of the probe unit to form the
recess which traverses from one side to the other of the cut
substrate.
The recess 12 has preferably a depth of 0.05 to 0.3 mm and a width
of 0.2 to 5 mm.
Next, a sacrificial film is filled in the recess. The sacrificial
film may be made of metal, resin such as epoxy and urethane, and
inorganic material such as inorganic salt. An example of the
inorganic salt is calcium carbonate.
It is necessary to set the thickness of the sacrificial film 14
thicker than the depth of the recess 12. It is preferable to set
the thickness to about 0.05 to 0.4 mm although it depends on the
substrate thickness and the recess thickness.
In the following description, it is assumed that the sacrificial
layer made of metal is used.
A plating underlayer (hereinafter called a recess plating
underlayer) 13 is formed on the whole surface of the substrate on
the recess side 12, for example, by sputtering. On this recess
plating underlayer, a sacrificial layer 14 is plated. The plated
metal is different from the metal of the lead, for example, copper.
If copper is used as the metal to be plated, chromium is sputtered
to form a tight adhesion layer. On this chromium layer, seed copper
may be sputtered. In this specification, the tight adhesion layer
and seed sputter layer are collectively called the plating
underlayer. The sacrificial layer of metal may be formed directly
by electroless plating without using the plating underlayer.
If the sacrificial film is to be made of metal, the cross sectional
shape of the recess 12 at both ends thereof is preferably smooth
and arc. The diameter R of the arc is preferably greater than the
depth of the recess. If the recess has a rectangular shape
constituted of the bottom surface and sides, voids may be formed in
the sacrificial film 14 filled in the recess having a plated
surface, during the plating growth process starting from the bottom
surface and sides. If the recess has the end shape which is smooth
and arc, voids are not formed in the sacrificial film 14 in the
recess 12.
As shown in FIG. 10B, the surface of the plated sacrificial layer
14 is polished to leave the sacrificial layer 14 only in the recess
12 and expose the substrate 1 in the other area. The whole polished
surface including the surface of the sacrificial layer is
preferably made flat.
FIG. 10C is a plan view of the substrate surface after
polishing.
If the substrate is an electroconductive substrate, after an
insulating layer is formed on the substrate surface in the area
where the recess is to be formed, the recess is formed in the
manner described above, then the recess plating underlayer is
formed on the whole substrate surface, and thereafter the
sacrificial layer is formed. As the surface of the substrate is
polished, the insulating film is exposed in the whole area other
than the recess area, and the sacrificial layer is left only in the
recess.
If epoxy resin or urethane resin is used as the material of the
sacrificial layer, a glass substrate, a ceramic substrate or a
metal substrate is used to selectively remove the sacrificial layer
at a later process. In this case, the shape of the recess wall is
not limited to a particular shape and may be rectangular.
Also in this case, excessive resin is filled in the recess to such
an extent that the resin overflows the recess. After the resin is
hardened, the substrate is polished to planarize the surface
thereof, to leave the resin only in the recess, and to expose the
substrate in the other area. For example, if epoxy resin is used,
this resin can be hardened by a heat treatment at 150.degree. C. If
resin is used as the material of the sacrificial layer, the time
required to form the sacrificial layer can be shortened
considerably as compared to forming the sacrificial layer by
plating.
If inorganic salt such as calcium carbonate is used as the material
of the sacrificial layer, inorganic salt powders are filled in the
recess without forming voids and dents, pressed and polished to
leave the sacrificial layer of inorganic material only in the
recess.
As shown in FIG. 10D, on the sacrificial layer 14, a bumping bar 9
is formed. The cross sectional shape of the bumping bar 9 along the
longitudinal direction of leads to be formed on the substrate is an
arc shape having a smooth upper surface. The bumping bar 9
traverses the substrate along the direction perpendicular to the
lead, exhibiting the same cross sectional shape over the whole
length. A dome-shaped projection constituting a portion of a sphere
may be formed in the front portion of each lead. The center of the
dome-shaped projection may be at the center of the width of each
lead front portion or at the position displaced from the lead to
raise the side of the lead.
In FIG. 10D, a cut to be formed at a later process is shown, the
cut extending from the bottom of the substrate 1 into the
sacrificial layer 14.
Next, a probe plating underlayer is formed on the polished surface
in an area where the probe lead is to be formed, preferably along
the direction perpendicular to the longitudinal direction of the
recess 12.
In this case, the probe plating underlayer is formed so that the
distal end of the probe plating underlayer corresponding to the
distal end of the probe lead is positioned on the dumping bar 9
formed on the sacrificial layer 14, or on the sacrificial layer 14
across the dumping bar 9, and that the remaining lead is positioned
only on the substrate on one side of the recess.
If the probe leads are to be formed in parallel at a constant
pitch, the probe plating underlayers are juxtaposed at the same
pitch.
The probe plating underlayer can be formed by known pattern forming
methods, such as a method of forming a metal probe underlayer on
the substrate whole surface and pattering it by a photo etching
process by using a resist mask and a method of printing conductive
paste on the substrate.
The juxtaposed probe plating underlayers are subjected to
electroplating by using plating liquid which contains sulfuric acid
as its base composition, to thereby grow leads 2.
The thickness of the grown metal lead is preferably about 10 to 80
.mu.m.
Another method of forming the leads may be performed as in the
following manner. A probe plating underlayer is formed on the whole
surface of the substrate with the bumping bar. Next, a resist
pattern is formed to expose the probe plating underlayer only in
the areas where the probe leads are to be formed. The exposed probe
plating underlayer is subjected to electroplating to grow
leads.
The probe plating underlayer in the areas where the leads are not
formed and the resist pattern are removed by milling. The leads 2
juxtaposed on the substrate 1 having the metal layer 14 filled in
the recess 12 can therefore be obtained.
FIG. 10E is a schematic diagram showing this state.
Metal to be plated may be nickel, nickel alloy such as Ni--W and
Ni--Fe, or metal glass, which gives proper rigidity and elasticity
to each lead.
As shown in FIG. 10D, a cut 15 is formed in parallel to a cross
section D-D' from the bottom of the substrate 1 into the
sacrificial layer 14. The cut extends over the whole width of the
substrate and does not cut the whole sacrificial layer 14. This cut
15 partitions the substrate into two parts. However, the two parts
are not separated because they are attached to the sacrificial
layer 14 in the recess and the leads 2. Next, as the sacrificial
layer 14 and recess plating underlayer 13 are removed by etching,
the two parts are separated. The front portion of each lead 2
becomes a resilient contact piece 3 curved and extended from the
edge of the substrate as shown in FIGS. 2A and 2B. The other
portion is firmly adhered to the substrate. A probe unit having
leads juxtaposed at a predetermined pitch can thus be formed.
If a plated pad or protective film is formed on the surface where
the lead is in tight contact with the substrate, the process
similar to the above-described embodiment is performed.
If a dome-shaped projection is formed at the distal end of each
lead and the above-described processes are performed, a probe unit
having the dome-shaped projections such as shown in FIGS. 3A and 3B
is obtained.
If the dome-shaped projection is formed at such a position that the
center of the dome is displaced from the lead and the side of the
lead having a portion of the dome is raised, a probe unit such as
shown in FIGS. 6A and 6B or FIGS. 7A and 7B can be obtained.
With the manufacture method described above, the cut does not reach
the probe lead 2 and a physical force of separating the leads 2 and
substrate 1 is not applied. A probe having leads regularly disposed
at a fine pitch can be obtained by patterning and plating growth
without damaging the probes. Since the curved portion of the probe
without edge portions is pushed against the electrode, the
electrode is hardly damaged.
The present invention has been described in connection with the
preferred embodiments. The invention is not limited only to the
above embodiments. It is apparent that various modifications,
improvements, combinations, and the like can be made by those
skilled in the art.
* * * * *